QinetiQ Proprietary
Integrated Radiation Mitigation
and Shielding Design
Pete Truscott, Ramon Nartallo, Fan Lei, Daniel
Heynderickx, Sebastien Bourdarie, Angelica SicardPiet
QinetiQ Space & Unmanned Vehicles
DH Consultancy
ONERA
18th January 2010
The work presented has been sponsored by
ESA (contract number 21290/08/NL/JK),
QinetiQ plc and UK Ministry of Defence
www.QinetiQ.com
© Copyright QinetiQ limited 2010
QinetiQ Proprietary
Effects of the Jovian Radiation Environment
• Significantly enhanced radiation environment compared with near Earth
− Particle energies and fluxes (electron energies beyond 100 MeV)
• Total ionising dose – microelectronics, MEMS, sensors, materials
• Total non-ionising dose (displacement damage) – sensors/FPA, solar arrays
• Deep dielectric charging
• Single event effects (upset, latch-up, burn-out, gate-rupture, etc)
• Several standard tools are not intended for use in this regime:
− SHIELDOSE (10MeV) and SHIELDOSE-2 is based on Monte Carlo data for up to 50MeV
− EQFLUX
• Environments in vicinity of Galilean moons
www.QinetiQ.com
© Copyright QinetiQ limited 2010
2
QinetiQ Proprietary
Effects of the Jovian Radiation Environment
Comparison with MEO (GIOVE solar max, 939 days)
1.E+09
Total ionising dose [rad(Si)]
1.E+08
Laplace total
Laplace trapped e-
Laplace brems
Laplace trapped protons
Laplace solar protons
GIOVE total
GIOVE trapped e-
GIOVE brems
1.E+07
Laplace total and trapped electrons
1.E+06
1.E+05
GIOVE total and trapped electrons
1.E+04
1.E+03
0
5
10
15
20
Al shield thickness [mm]
Data from J Sørensen and G Santin (Laplace), and QinetiQ (GIOVE, VALCOMPT project)
www.QinetiQ.com
© Copyright QinetiQ limited 2010
3
QinetiQ Proprietary
Review of mitigation measures
• Shield
− Judicious positioning of more sensitive equipment to shield using less sensitive systems
− Compact system distribution
− Addition of deliberate shielding (at equipment box level, spot shielding, thicker cover glasses …)
− “Radiation vault” design
• Component and technology selection
− Radhard / Rad-tolerant
− Exploit difference in tolerances due to different
commercial designs
− Watch-out for potential effects of new (especially
high-Z materials) introduced in microelectronics!
• Hardening at circuit level
− Less susceptible to effects of e.g. voltage shifts
− Circuit compensation for e.g. threshold shifts,
gain drift
− EDAC
www.QinetiQ.com
© Copyright QinetiQ limited 2010
4
QinetiQ Proprietary
Review of mitigation measures
• Provision for annealing
− Particularly for scientific instrument technologies
• Duty cycling & cold redundancy
− Mitigate some TID effects by unpowering equipment during intense irradiation periods
• Hide
Mitigation for internal or deep dielectric charging
• Shield
• Reduction in material thickness / selection of dielectric
• Ensure common grounding
• De-rating of electrical/electronics systems (reduce-f, filter)
• Avoid cold temperatures
www.QinetiQ.com
© Copyright QinetiQ limited 2010
5
QinetiQ Proprietary
Shielding and influence of shielding materials
•
Shielding in context of Al? Why?
•
High-Z materials better at scattering electrons
•
However, per unit mass, high-Z materials also
− Have lower stopping powers (fewer electrons per unit
mass)
− Generate more bremsstrahlung (cross-section scales
as Z2)
•
Graded shields use combinations of low and
high-Z materials to:
− Efficiently stop electrons with low bremsstrahlung
production (low-Z)
− Efficiently absorb any bremsstrahlung, and scatter
any residual low-energy electrons
(1)
Sensitive volume
(2) e
e-

(3) e
(4) e
Low-Z
Hi-Z
Low-Z
− Absorb any residual photoelectrons or Auger
electrons
•
Provide significant mass-saving for electron
environments
www.QinetiQ.com
© Copyright QinetiQ limited 2010
6
QinetiQ Proprietary
Graded shielding example for GIOVE orbit
1 year at solar maximum
1.E+07
1.E+06
eqv 1.0 mm Al
eqv 1.5 mm Al
eqv 2.0 mm Al
eqv 2.5 mm Al
Total ionising dose [rad(Si)]
Total ionising dose [rad(Si)]
Eqv. 0.2-0.8 mm Al
1.E+06
1.E+05
eqv 0.2 mm Al
eqv 0.3 mm Al
eqv 0.4 mm Al
eqv 0.5 mm Al
eqv 0.6 mm Al
eqv 0.8 mm Al
1.E+04
0
20
40
60
80
100
Eqv. 1.0-2.5 mm Al
1.E+05
1.E+04
1.E+03
0
Percentage aluminium by weight
20
40
60
80
100
Percentage aluminium by weight
Total ionising dose [rad(Si)]
1.E+05
Eqv. 2.5-5.0 mm Al
1.E+04
1.E+03
eqv 3.0 mm Al
eqv 3.5 mm Al
eqv 4.0 mm Al
eqv 4.5 mm Al
eqv 5.0 mm Al
1.E+02
0
20
40
60
Percentage aluminium by weight
80
100
© Copyright QinetiQ limited 2010
www.QinetiQ.com
7
QinetiQ Proprietary
Graded shielding example for GIOVE orbit
1 year at solar maximum
50%
Pure aluminium shield
Pure tantalum shield
Optimised shield
Optimised/Pure-Al TID
1.E+06
45%
40%
35%
1.E+05
30%
25%
1.E+04
20%
15%
1.E+03
10%
5%
1.E+02
Optimised shield TID / Pure Al
shield TID
Total ionising dose [rad(Si)]
1.E+07
0%
0.1
1
10
Equivalent thickness of aluminium [mm]
www.QinetiQ.com
© Copyright QinetiQ limited 2010
8
QinetiQ Proprietary
Radiation dose versus depth in spherical Al shields
1.E+08
Total
Trapped electrons
Bremsstrahlung
Trapped protons
Solar protons
Total ionising dose [rad(Si)]
1.E+07
1.E+06
1.E+05
1.E+04
1.E+03
0
5
10
15
20
Al shield thickness [mm]
Data from J Sørensen and G Santin
www.QinetiQ.com
© Copyright QinetiQ limited 2010
9
QinetiQ Proprietary
Comparison of TID for Al, Fe and Ta slab shields
NOTE: Based on earlier (Jan 2009) spec for environment
Ganymede science mission dose
[rad(Si)/day]
1.E+04
Al slab sield
Ta slab shield
Fe slab shield
1.E+03
This
requires further, more thorough analysis
1.E+02
1.E+01
Note this is at expense of higher bremsstrahlung
1.E+00
0
2
4
6
8
10
Equivalent thickness of Al for similar mass [mm]
www.QinetiQ.com
© Copyright QinetiQ limited 2010
10
QinetiQ Proprietary
Beware of dose enhancement effects
In environments which are photon /
bremsstrahlung-dominated, dose
enhancement effects are a risk
• High-Z materials produce low-energy
photo- and Auger e- in bremsstrahlung
environment
• Very localised enhancement of dose
• Au contacts, W-vias and silicides (WSi)
e-

Au
Si
www.QinetiQ.com
© Copyright QinetiQ limited 2010
11
QinetiQ Proprietary
Beware of dose
enhancement effects
• Detailed Geant4 microdosimetry
analysis performed for Cu
metallization layer
• Need to use MC tools like MULASSIS
Cu metallisation
Al metallisation
Cu/Al
1.E-08
8
7
6
5
1.E-09
4
1.E-10
3
2
1.E-11
Note: Most TID testing
performed near this energy
1.E-12
1.E+00
© Copyright QinetiQ limited 2010
1.E+01
1.E+02
Photon energy [keV]
Dose enhancement factor Cu/Al
Dose per unit fluence [rad(SiO2)cm2]
1.E-07
1
0
1.E+03
www.QinetiQ.com
12
QinetiQ Proprietary
ESA JORE2M2 Project (Jovian Radiation Environment and
Effects, Models and Mitigation) Objectives
•
Assess the requirements for radiation and plasma environment models, and
effects and mitigation tools for future Jupiter-system missions (including
Jupiter flyby).
•
Review the available models and tools used to predict the Jovian radiation
and plasma environments and their effects, and identify a strategy for
software development and update.
•
Design, develop, validate and install at a model for predicting the
environment within the Jovian magnetosphere (including the Galilean moons),
and effects and mitigation tools. The tools shall permit assessment of
radiation-related quantities for engineering purposes, including where
possible, confidence levels.
•
All tools and models will be such as to allow operation over the Internet
(World-Wide Web), and are to be compatible data interfaces with SPENVIS.
www.QinetiQ.com
© Copyright QinetiQ limited 2010
13
QinetiQ Proprietary
Effects Tools Questionnaire
Which existing models do you know or which ones do you use to define Jupiter radiation
environment?
Current use:
Relevant for future use:
•
SHIELDOSE / SHIELDOSE-2
•
MULASSIS
•
SSAT
•
GEMAT
1
1
•
FASTRAD
5
2
•
OMERE
3
1
•
DOSRAD
3
2
•
NIEL (within SPENVIS)
4
2
•
EQFLUX
2
1
•
GRAS
2
2
•
DICTAT
6
3
•
Others include SPIS, Tiger/MCNP, NUMIT
8
4
6
2
2
2
www.QinetiQ.com
© Copyright QinetiQ limited 2010
14
QinetiQ Proprietary
Effects Tools Questionnaire
Which radiation effects are you interested in and what are their relative importances?
Not imp. :
Quite imp.:
Very imp.:
•
Total Ionising Dose (TID)
0
1
9 SD2/ML
•
Non-Ionising Energy Loss (NIEL)
0
5
5 ML
2
1
5
(to microelectronics)
•
Non-Ionising Energy Loss (NIEL)
EQFLUX
(to solar arrays)
•
Single Event Effects (SEE)
8 GEMAT
0
2
•
Sensor background effects
2
2
6 GEMAT
•
Surface charging
1
4
4
•
Deep-dielectric charging
1
3
6 DICTAT
•
Need
both web-based
tools and local applications which deal with radiation effects
Other:formaterial
degradation
•
Operating systems: ~75% Windows, ~25% Linux (but also one expression of interest in Mac-based
solution!)
www.QinetiQ.com
© Copyright QinetiQ limited 2010
15
QinetiQ Proprietary
JORE2M2 Project Integrated Solution for Environment and
Effects Simulation for Jupiter Missions
• Coherent set of interfaced tools to simulate environment and effects in a SPENVIScompatible framework
• JOSE for energetic environment, and Divine + Garrett plasma models
• Requirement to extend existing engineering tools, in particular generate new
SHIELDOSE-2 database which:
− Extends the energy range for electrons to >50MeV
− Allows treatment of non-Al shields
• Allow modelling of radiation environment at moons, taking into consideration influence
of intrinsic and induced fields as well as structure of the moons (PLANETOCOSMICSbased)
• Development of genetic algorithm software to optimise 1-D shields (composition and
thickness)
• Standard tools such as DICTAT and GEMAT are also to be available within Framework
www.QinetiQ.com
© Copyright QinetiQ limited 2010
16
QinetiQ Proprietary
SHIELDOSE-2 Enhancement Shield and target materials
Shield materials
• Al, Ta, Fe
• 1mm Al followed by Ta
• CW80 and Ti
Targets - Materials in which energy is considered deposited (TID)
• Al, Si, H2O, SiO2, C (graphite), bone, CaF2, GaAs, LiF, tissue (in SHIELDOSE-2).
• plastics to represent polyimide (C22H10O5N2 1.42 g/cm3), and epoxy (C18H19O3,
1.85 g/cm3).
• HfO2, SiC, and InGaAs (assumed In0.5Ga0.5As), HdCdTe (assumed to be Hg0.7Cd0.3Te
for MWIR sensors), NaI, MgO, CdZnTe (Cd0.96Zn0.04Te for LWIR sensors) and Ge.
Targets - Materials in which energy is considered deposited (TNID)
• Si and GaAs (based on ECSS-E-10-12 NIEL coefficients)
www.QinetiQ.com
© Copyright QinetiQ limited 2010
17
QinetiQ Proprietary
SHIELDOSE-2 Enhancement Dose predictions for Ta slab
shield: Laplace science mission (Env specification v1.0)
Ganymede mission TID [rad(Si)/day]
1.E+04
MULASSIS Dose: 0.5-100MeV
SHIELDOSE-J Dose: 0.5-100MeV
SHIELDOSE-J Electron Dose
1.E+03
1.E+02
1.E+01
1.E+00
0
1
2
3
4
5
Slab shield thickness [mm]
www.QinetiQ.com
© Copyright QinetiQ limited 2010
18
QinetiQ Proprietary
Genetic Algorithm-based shielding tool
• Uses a genetic algorithm
software package +
MULASSIS to help identify
optimal shield configurations
• Use cases
− Case 1: Identify lowest-mass
design meeting a specific
shielding performance
− Case 2: Best shielding
performance for a given areal
mass budget
www.QinetiQ.com
© Copyright QinetiQ limited 2010
19
QinetiQ Proprietary
PLANETOCOSMICS Enhancement Galilean Moon
Environment Tool
Update L Desorger’s PLANETOCOSMICS model, which simulates particle
interactions in planetary magnetic fields and atmospheres
Use-cases:
1. Treat the radiation environment at the Galilean moons, including:
• particle propagation in internal/induced magnetic + uniform field representing Jovian
field
• predictions of the trapped radiation levels at the surface of the moons
• Treatment of secondary radiation backscatter (albedo) from the surface
• Outputs should be particle fluence spectra and ionizing and non-ionising dose.
2. Determine cutoff rigidities in the Ganymede internal magnetic field
• Apply to Jovian electron and proton fluence
www.QinetiQ.com
© Copyright QinetiQ limited 2010
20
QinetiQ Proprietary
PLANETOCOSMICS Enhancement Motion of electrons in
Ganymede field
5MeV
10MeV
20MeV
50MeV
www.QinetiQ.com
© Copyright QinetiQ limited 2010
21
QinetiQ Proprietary
PLANETOCOSMICS Enhancement Motions of electrons in
Europa field (15MeV electrons)
www.QinetiQ.com
© Copyright QinetiQ limited 2010
22
QinetiQ Proprietary
PLANETOCOSMICS Enhancement Depletion of trapped
radiation belts
• Added complexity from the slower orbital
period of Europa with respect to the
combined effects:
− rotation of the Jovian magnetic field
− drift period of the particles
• Since the field lines of Jupiter’s sweep
from the trailing hemisphere to the leading
hemisphere, the plasma overtakes the
moon, resulting in
− particle deposition in the trailing hemisphere
− Depleted particle populations at leading
hemisphere
www.QinetiQ.com
© Copyright QinetiQ limited 2010
23
QinetiQ Proprietary
PLANETOCOSMICS Enhancement Depletion of trapped
radiation belts
• Algorithm included to calculate the drift of
particles relative to the moons between
bounce
• No need to simulate whole of Jupiter field
• 15 MeV e- shown
Europa
Ganymede
www.QinetiQ.com
© Copyright QinetiQ limited 2010
24
QinetiQ Proprietary
Summary
• Jupiter system environment presents a unique, hostile radiation threat to future
missions
• Range of traditional methods for mitigation and also more innovative solutions
• Use of high-Z shields could offer significant mass savings
− Electron penetration may not make it appropriate to consider graded shields
− Other practical issues?
• Beware of subtleties in testing for electron/X-ray environment?
• JORE2M2 Project leading to an integrated system of tools to model environment and
effects for future Jupiter system missions
• On effects side:
− Rapid calculation of dose (TID/TNID) for new shields/targets through updated SHIELDOSE2
− Shield optimisation models
− Moon environment simulation based on comprehensive Geant4 physics
www.QinetiQ.com
© Copyright QinetiQ limited 2010
25
QinetiQ Proprietary
Backup slides
www.QinetiQ.com
© Copyright QinetiQ limited 2010
26
QinetiQ Proprietary
General Susceptibilities of Microelectronics Technologies
TID effects
Semiconductor technology
Ionisation failure threshold
rad(Si)
ECL
>105
Bipolar
105 upwards*
Standard TTL
>105
I2L
105
bipolar linear
Approximately 104 - 105
PMOS
104 upwards
NMOS
103
bulk CMOS
3x103 – 105
CMOS/SOS – SOI (commercial)
>104?
CMOS/SOS – SOI (rad-hard)
106 upwards
Commercial CCDs
103-104
*Bipolar technology subject to adverse dose-rate dependent TID effects.
www.QinetiQ.com
© Copyright QinetiQ limited 2010
27
www.QinetiQ.com
© Copyright QinetiQ limited 2010